The invention relates to an apparatus for freezing liquid-carrying pipes, with an annular casing having an inwardly open cross-section, with a supply line, provided with a valve, for supplying a refrigerant to the interior of the casing.
In the case of repairs or installation measures on liquid-carrying pipes or lines, particularly heating pipes, such as when fitting regulating or control valves or replacing heaters and the like, to avoid the need for shutting down the complete heating plant and emptying the pipe or line is frozen, so that a solid plug is formed therein. This is brought about in that a sleeve is placed around the pipe and into it is introduced the refrigerant. Apparatuses exist in which the refrigerant is produced by a heat pump and circulates in a closed circuit through the sleeve and is conveyed back to the heat pump. In another construction there is no circulation of the refrigerant and it instead passes out of a storage bottle or cylinder through the sleeve and an outlet port therein into the environment. The outlet port can optionally be provided with a hose, so that part of the refrigerant can be led away into the open from the freezing and working point and optionally out of a room or the like. The non-removed quantity, of refrigerant such as chlorinated hydrocarbons, constitute a potential hazard for workers, particularly when carrying out soldering and/or welding. The known sleeve-like casing of the apparatus can be open towards the pipe and together with the latter forms a cavity around the same, into which the refrigerant is introduced and can come into direct contact with the outer wall of the pipe, which increases effectiveness. Known apparatuses, which in part do not fulfill the latter requirement are known from the following publications U.S. Pat. Nos. 2,483,082, 2,572,555 and 3,559,423DE-OS No. 16 00 607, DE-OS No. 23 30 807, German utility model 81 06 063 and British Patent No. 1 209 144.
All these apparatuses operate with a liquid refrigerant, which optionally evaporates and in part, particularly in the case of circulation, remains in the liquid phase, but in no case solidifies.
The need to recirculate the refrigerant is disadvantages due to the costs involved, whereas, if the refrigerant, namely the chlorinated hydrocarbons have to be discharged into the environment, it is prejudicial to the latter, so that the use of chlorinated hydrocarbons is no longer desired and is in part forbidden. If the casing of the sleeve surrounding the pipes as such, without the pipe, is completely closed and, consequently, has an inner wall, the action is made worse, because the heat transfer must take place via the inner wall.
The latter disadvantage also remains in the apparatus according to German Patent No. 601 278, which operates with solid carbon dioxide. The latter is introduced in this form through the relatively large openings provided on the end walls of the casing and which are subsequently closed. The casing has vents in the form of vent valves.
The use of liquid carbon dioxide, which only ices in the vicinity of the pipe line to be frozen and forms carbon dioxide snow is possible as a result of a stable sleeve placed around the pipe and with a flexibile pipe seal formed as a function of the pipe diameter. It has proved that such a sleeve is not practical and is disadvantageous, which is partly due to the aforementioned construction. As the carbon dioxide in the vicinity of the outer jacket of the sleeve enters the cavity formed between the sleeve and the pipe and therefore remote from the actual pipe, the dry ice initially preferably forms directly around the pipe and between the latter and the supply opening, so that an insulating layer is formed round the pipe. The dry ice layer on the pipe surface initially evaporates, but is still enveloped by the dry ice and can consequently not escape. Thus, it forms a gas gap insulating layer between the dry ice and the pipe, which further reduces the effectiveness of icing. The refrigerant supply opening is located in the outer jacket of the sleeve and is blocked by the formation of the dry ice layer. In order that the ice plug formed can be forced out, the carbon dioxide must be supplied under high pressure. This cannot take place continuously for technical and economic reasons, so that carbon dioxide is only supplied at certain intervals, which also impairs efficiency.
In order to bring about an improvement a flexible, non-self-supporting sleeve in the form of a jacket has been chosen, which is placed around the pipe and fixed round the pipe wall by strings or cords. This leads to a flexible bag sleeve, which only partly removes the disadvantages of the aforementioned sleeve. The gas gap insulating layer between the dry ice and the pipe wall which also forms in the case of the bag sleeve can partly be eliminated in that every so often the outer wall of the bag sleeve is intensely manually kneaded. However, this is very disadvantageous due to the pronounced cooling action of dry ice. The constant kneading also very disadvantageously influences the quality of the bag sleeve. The use of this bag sleeve is very complicated and does not alter anything as regards the long freezing times and the high carbon dioxide requirement of such sleeves. As a result of the clogging and freezing up of the inlet port, it is not possible to supply the carbon dioxide in a regulated, reduced quantity and must instead be supplied at a considerable pressure with a wide open feed valve, with a carbon dioxide quantity which is excessive by the plug icing up the opening, so that here again the supply must take place at intervals.
The aim underlying the invention essentially resides in avoiding the aforementioned disadvantages by an apparatus having a self-supporting casing sleeve, which permits an effective icing of a pipe by liquid carbon dioxide.
According to the invention, an apparatus of the aforementioned type is provided wherein the casing has two parts which can be directly fixed or braced together substantially at right angles to the casing axis with, in each case, end walls kept spaced by a jacket wall and a carbon dioxide supply lance can be engaged with its end face having a nozzle opening with the connecting face of the inside edges of the end walls.
Unlike in the case of one-part casings, the two-part construction leads to a symmetrical bracing in two diametrically facing areas, corresponding sleeve sizes being obtained for corresponding pipe masses, so that a better fixing and sealing can be achieved of the type necessary when using liquid carbon dioxide. Due to the fact that the frontal opening of the lance can be brought up to the circumferential area of the edges of the casing end walls, it is ensured that the opening of the lance issues directly over the wall of the icing pipe. Thus, carbon dioxide constantly flows along the pipe in the form of a film, partly in liquid and partly in gaseous form, whereas solid carbon dioxide only forms as an insulating layer between said film and the outer jacket wall of the casing, but is not deposited directly on the wall of the icing pipe. This leads to higher effectiveness of the icing, in that the heat absorption of the environment is reduced, whereas that of the pipe is increased, the absorbed heat evaporating the liquid supplied carbon dioxide and which, despite a fixing of the casing parts to the pipe, flows out particularly in the resulting connecting area. Additionally it would be possible to provide an outlet port having a regulating valve, which would preferably diametrically face the inlet port for the carbon dioxide. The lance can be fixed in the jacket wall of the casing along its axis and project into the aforementioned area. However, according to a preferred embodiment, the lance is fixed by frictional resistance in an opening of the jacket wall of a casing part, so that it is possible to ensure even under different bracing conditions and different pipe thicknesses for which a casing can be used to a restricted extent, a mounting of the end face of the lance on the wall of the pipe to be iced.
According to another preferred embodiment the valve in the supply line is a ball valve, which has a small passage opening in the ball corresponding to an economic carbon dioxide passage quantity for all pipes to be frozen. Icing makes a conventional poppet valve very difficult and possibly even impossible to operate.
The inlet port in the end face of the carbon dioxide supply lance is preferably a fine nozzle with a diameter between 0.5 and 1.0 mm, because with a given refrigerant supply quantity the latter flows in with an adequate and in particular higher speed than with an earlier opening and therefore improves the flow round the pipe wall.
Although the two casing parts can engage over or in one another in different ways, in that they are e.g. identically constructed and one casing part overlaps on one side and the other on the other side, according to a preferred embodiment the external diameter of the jacket wall of one of the casing parts corresponds to the internal diameter of the jacket wall of the other casing part and the spacing of the outsides of the end walls of one casing part corresponds to the spacing of the insides of the end walls of the other casing part.
This leads to a reliable, tight connection of the two casing parts during and after fixing round a pipe. The fixing of the casing parts to a pipe preferably takes place by screws provided with nuts or screw-nut connections. In preferred manner, the casing parts have substantially radially and longitudinally extending tongues, which are provided with openings, through which can be passed screws and onto which can be screwed nuts. The holes in the tongues of one of the casing parts are in particular elongated slots or holes. So that the heads of the screw and nut are located in a flat and planar manner on the tongues, according to a further development the lateral faces of the tongues remote from the adjacent flange of the in each case other casing part are parallel to one another. The tongues taper from their connection side with the actual casing to the free side thereof in a trapezoidal manner, the facing lateral faces being directed substantially radially by tongues interconnected by a screw. While the circumferential extension of the two casing parts can fundamentally differ and e.g. the circumferential extension of the casing part engaging in the other part is greater than the part overlapping it, so that the tongues can be substantially aligned on in each case one casing part, according to a preferred development the casing parts extend substantially over the same circumferential angle range. To ensure an adequate fixing area, the tongues are arranged in angularly displaced manner on the casing parts, so that the circumferential spacing of the tongues of the inner casing part is smaller than that of the overlapping casing part. An optimum angular range for the circumferential extension of the casing parts is 210.degree..
The inventive apparatus provides the possibility of an all-around icing of pipes by carbon dioxide, which obviates the disadvantages of the prior art and, in particular, permits an effective icing also with respect to the aforementioned crimped sleeve. For the same test conditions, shorter icing times and carbon dioxide consumption quantities have been noted. Compared with the known self-supporting sleeves only usable with other liquid refrigerants, the inventive construction of the icing casing significantly reduces the icing time and offers considerable economy with the refrigerant costs involved. As a result of the ball valve provided it is possible to have a continuous regulated supply also of carbon dioxide with a constant supply rate. This ensures that the frozen ice plug will remain in the pipe throughout the working period.
Further advantages and features of the invention can be gathered from the claims and description relative to a non-limitative embodiment and the attached drawings.